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Author: Subject: Salting out Methanol
wackyvorlon
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[*] posted on 16-4-2016 at 12:34
Salting out Methanol


Recently I bought a jug of -40 car windshield washer fluid with the plan to extract some methanol from it. With distillation, I've managed to get about 300ml of 90% ethanol. To reach this point required distilling twice, which is pretty time consuming.

I decided to try salting out the methanol, some googling lead me to believe that I could do so with sodium chloride. I made up a saturated solution of sodium chloride, and added 50ml of that to 50ml of methanol in a 125ml sep funnel. I shook and vented a few times, then let it sit. Almost immediately the salt came out of solution. I've attached a picture, I'm going to say that it seems that this is not a viable method of removing the remaining 10% of water. Any suggestions?

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ParadoxChem126
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[*] posted on 16-4-2016 at 20:02


In this example, methanol has a greater affinity for water than sodium chloride does. As a result, the methanol forces the salt out of solution, not the other way around.

To increase the concentration from 90%, fractional distillation and/or molecular sieves can be used.
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JJay
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[*] posted on 16-4-2016 at 21:07


Fractional distillation should remove almost all of the water if you go slow. I'm distilling some methanol as we speak, but I usually get mine from dry gas (which probably doesn't even require distillation, but I'm doing it just in case there are additives).
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BromicAcid
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[*] posted on 16-4-2016 at 21:30


Quote: Originally posted by wackyvorlon  
With distillation, I've managed to get about 300ml of 90% ethanol.


You should still be able to edit your post to correct this to methanol. Interesting note is just because this does not work with sodium chloride, does not mean salting out is off the table. As ParadoxChem said, in this instance the methanol has a greater affinity for the water, or as I look at it, the water has a greater affinity for the methanol than the sodium chloride. Anyway, there is a thread kicking around here somewhere where chemists are salting ethanol out of water. Although I would think it would be even more difficult to salt out the methanol, there might be some good salts to try in that thread.

http://www.sciencemadness.org/talk/viewthread.php?tid=61746

http://www.sciencemadness.org/talk/viewthread.php?tid=24299




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macckone
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[*] posted on 17-4-2016 at 10:29


Anydrous epsom salt is likely to work better. But it will absorb some methanol as well. Potassium carbonate works with high proof ethanol, that might work as well.
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CaptainPike
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[*] posted on 26-4-2016 at 10:52


Fractional Crystallization!
If only 10% water remains, try putting it in your freezer. The water ice might freeze out, filter with cold apparatus.
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[*] posted on 26-4-2016 at 11:15


Quote: Originally posted by CaptainPike  
Fractional Crystallization!
If only 10% water remains, try putting it in your freezer. The water ice might freeze out, filter with cold apparatus.

Are you aware that one of the uses of methanol is as an anti-freeze?
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macckone
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[*] posted on 26-4-2016 at 19:50


That might work with butanol or pentanol but not lower alcohols.
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Radagast97
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[*] posted on 27-4-2016 at 12:59


Quote: Originally posted by CaptainPike  
Fractional Crystallization!
If only 10% water remains, try putting it in your freezer. The water ice might freeze out, filter with cold apparatus.


Wrong side of the phase diagram. MeOH has a higher freezing point than MeOH with 10% water.

Second, your freezer better go down to ~-100C.
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[*] posted on 27-4-2016 at 14:00


Quote: Originally posted by BromicAcid  
http://www.sciencemadness.org/talk/viewthread.php?tid=61746

I'd forgotten about that, and it is not so long ago.

Needs re-visiting, certainly.




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